Conventionally, there have been proposed various compressors for compressing a compression medium such as refrigerant in a refrigeration machine, and among these compressors, screw compressors have less vibration and noise than reciprocating compressors and are used for various purposes.
The twin screw compressor described in Japanese Patent Publication No. 8-74764 is equipped with a female rotor having helical flutes, a male rotor having helical lobes that mesh with the helical flutes in the female rotor, and a casing that houses the female rotor and the male rotor. The male and female rotors rotate while meshing inside the casing, whereby a compression medium is compressed inside an operation chamber (compression chamber) formed in the helical flutes, and is thereafter discharged from a discharge port in the casing.
In this twin screw compressor described in Japanese Patent Publication No. 8-74764, the operation chamber and a discharge channel are communicated through a notch before the operation chamber opens, so that the pressure difference between inside and outside is alleviated until the operation chamber opens, and the occurrence of pressure waves at the time when the operation chamber opens is controlled. Further, the time period of the start of communication is made irregular, whereby the interval of discharge operation that was a meshing frequency is made irregular and resonance of a discharge tube and structural body is prevented.
On the other hand, the single screw compressor described in Japanese Patent Publication No. 2002-202080 is equipped with a cylindrical screw rotor having plural helical flutes in its outer peripheral surface, at least one gate rotor that rotates while meshing with the screw rotor, and a casing that houses the screw rotor. A compression medium such as refrigerant is sent to the helical flutes in the screw rotor rotating inside the casing, and is compressed inside a space enclosed by the helical flutes, the teeth of the gate rotor and the casing, and is discharged from a discharge port in the casing.